West Nile virus threat remains

Since a blistering heat wave has settled over Southeast Missouri driving afternoon temperatures over 100 degrees, many Stoddard County residents aren't venturing outdoors until sunset.

That is why both the Missouri Department of Health and Human Services (DHSS) and the University of Missouri Extension are urging people across the state to remember that while not as common as it may have been three years ago, the threat of West Nile Virus (WNV) is still very real.

"Human WNV infections in Missouri typically occur around the end of July and continue until well into the fall," said Richard Houseman, assistant professor of entomology at the University of Missouri-Columbia.

Reported human cases of WNV peaked in Missouri in 2002 at 168 cases in 29 counties that resulted in seven deaths, according to the Centers for Disease Control (CDC). In 2003, that number dropped to 64 reported cases in 25 counties, but there were eight deaths and in 2004, there were 36 reported cases in 15 counties with two fatalities.

In 2005, according to the CDC, there were 30 cases in 17 counties and three fatalities. While the numbers may be dropping, Houseman cautions residents about feeling a false sense of security.

"It hits a susceptible population and then later, when it hits again, that population is not so susceptible," said Houseman. "The downturn is probably related to an increased immunity in the human and animal populations, but you should still take precautions."

So far this year, according to the CDC, nine counties in Missouri have reported birds or mosquitoes that have tested positive for WNV, including in Cape Girardeau County.

The bird was collected in June and tested positive for the virus at the Missouri Department of Health and Senior Services lab in Jefferson City, according to Charlotte Craig, director of the county health center.

"We found it here and thought we ought to get it tested," she said. "We mainly did it out of curiosity. We hadn't tested any birds yet this year, and it's better to know early."

A 67-year-old Jasper County man was hospitalized with probable WNV. He recovered. Horses in Miller, Howell, Dallas, Pulaski and Oregon counties have all tested positive for the virus. The number of horses infected has declined in recent years in large part to a vaccine for the disease. There is no vaccine for humans.

Jeff Myers, superintendent of the Dexter Street Department, said that the city is taking a new approach to eradicating mosquitoes this year.

"We are using a new chemical instead of the malathion we have been using," said Myers. "Now we use a chemical called Aqua-Reslin that is a permethrin-based chemical."

Although the new chemical is more costly, said Myers, it is safer to use and is much more effective.

"With the old stuff, it would take so many hours to have any affect on the mosquitoes," said Myers. "This chemical kills them almost instantly and not just mosquitoes, any insect in the air, including houseflies."

A chemical known as Agnique is also being put into the city's standing water sources, according to Myers. He said that the chemical comes in both spray and tablet forms and kills the mosquito eggs before they have a chance to hatch.

"We started this several months ago," said Myers. "The chemical stays in the water for three weeks and so we go out and reapply it every three weeks."

Myers said that the city has mosquito traps that they maintain and use the monitor the mosquito population across town. Since switching chemicals, Myers said there has been a significant decline in the number of mosquitoes trapped.

"I really want to thank Mark Stidham and the Board of Alderman and the mayor," said Myers. "They have given me more money in my budget for this which has allowed us to make these improvements."

Myers said that spray trucks made their rounds through the city nightly, beginning at 8:30 or 8:45 p.m. and not wrapping up until around 11:30 p.m.

The majority of human WNV cases -- which are transferred to humans through mosquitoes who have fed off an infected bird -- go unreported because they produce no symptoms or just mild symptoms that mimic the common cold.

Symptoms of West Nile are similar to other illnesses. They can include fever, severe headache, chills and body ache, Craig said. Some people may develop a rash or swollen lymph glands. In more severe cases people may experience nausea, difficulty swallowing, vomiting, drowsiness, confusion, a decreased level of consciousness, tremors, lack of coordination, muscle weakness and paralysis. If symptoms result, contact a physician.

In order to protect yourself during the height of the mosquito season, Houseman urges people to apply insect repellent to exposed skin and clothing, and when weather permits to wear long-sleeved shirts and long pants when outside. The CDC recommends products containing DEET, which provides longer-lasting protection. Mosquitoes are most active at dawn and dusk, so avoid being outdoors during those times if possible, Houseman said. Place mosquito netting over infant carriers and make sure windows and door screens are installed or in good condition, he said.

Perhaps most important is keeping the mosquito population down by keeping your property free of standing water, which provides a breeding ground. Flower pots, pet water dishes, birdbaths, swimming pool covers, buckets and barrels should be emptied at least once a week, she said. Remove discarded tires and other items that can collect water.

"If standing water can't be eliminated, such as in ponds or lakes, use a thin coat of mineral or light oil in the water to prevent the mosquito larvae from developing," Houseman said. "Oils should be applied in shallow margins of water where there is emergent vegetation. That is where most of the larvae will be."

Sacha Champion may be reached via e-mail at schampion@dailystatesman.com